<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
  <head>
    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
    <title>Transactional Cursors</title>
    <link rel="stylesheet" href="gettingStarted.css" type="text/css" />
    <meta name="generator" content="DocBook XSL Stylesheets V1.73.2" />
    <link rel="start" href="index.html" title="Getting Started with Berkeley DB Transaction Processing" />
    <link rel="up" href="usingtxns.html" title="Chapter 3. Transaction Basics" />
    <link rel="prev" href="nestedtxn.html" title="Nested Transactions" />
    <link rel="next" href="txnindices.html" title="Secondary Indices with Transaction Applications" />
  </head>
  <body>
    <div xmlns="" class="navheader">
      <div class="libver">
        <p>Library Version 11.2.5.3</p>
      </div>
      <table width="100%" summary="Navigation header">
        <tr>
          <th colspan="3" align="center">Transactional Cursors</th>
        </tr>
        <tr>
          <td width="20%" align="left"><a accesskey="p" href="nestedtxn.html">Prev</a> </td>
          <th width="60%" align="center">Chapter 3. Transaction Basics</th>
          <td width="20%" align="right"> <a accesskey="n" href="txnindices.html">Next</a></td>
        </tr>
      </table>
      <hr />
    </div>
    <div class="sect1" lang="en" xml:lang="en">
      <div class="titlepage">
        <div>
          <div>
            <h2 class="title" style="clear: both"><a id="txncursor"></a>Transactional Cursors</h2>
          </div>
        </div>
      </div>
      <p>
            You can transaction-protect your cursor operations by
            specifying a transaction handle at the time that you create
            your cursor.  Beyond that, you do not ever
            provide a transaction handle directly to a cursor method.
        </p>
      <p>
            Note that if you transaction-protect a cursor, then you must
            make sure that the cursor is closed before you either commit or
            abort the transaction. For example:
        </p>
      <pre class="programlisting">#include "db_cxx.h"

...

int main(void)
{
    // Environment and database opens omitted
    ...

    DbTxn *txn = NULL;
    Dbc *cursorp = NULL;

    try {

        Dbt key, data;
        key.set_data(keystr);
        key.set_size((strlen(keystr) + 1) * sizeof(char));
        key.set_data(datastr);
        key.set_size((strlen(datastr) + 1) * sizeof(char));

        DbTxn *txn = NULL;
        myEnv.txn_begin(NULL, &amp;txn, 0);
        try {
            // Get our cursor. Note that we pass the transaction handle 
            // here.
            db.cursor(txn, &amp;cursorp, 0); 

            // Perform our operations. Note that we do not pass a 
            // transaction handle here.
            char *replacementString = "new string";
            while (cursor-&gt;get(&amp;key, &amp;data, DB_NEXT) == 0) {
                data.set_data(void *)replacementString);
                data.set_size((strlen(replacementString) + 1) * 
                    sizeof(char));
                cursor-&gt;put(&amp;key, &amp;data, DB_CURRENT);
            }

            // We're done. Commit the transaction.
            cursor-&gt;close();
            txn-&gt;commit(0);
        } catch (DbException &amp;e) {
            std::cerr &lt;&lt; "Error in transaction: "
                       &lt;&lt; e.what() &lt;&lt; std::endl;
            cursor-&gt;close();
            txn-&gt;abort();
        }

    } catch(DbException &amp;e) {
        std::cerr &lt;&lt; "Error opening database and environment: "
                  &lt;&lt; file_name &lt;&lt; ", "
                  &lt;&lt; envHome &lt;&lt; std::endl;
        std::cerr &lt;&lt; e.what() &lt;&lt; std::endl;
    }


    return (EXIT_SUCCESS);
} </pre>
    </div>
    <div class="navfooter">
      <hr />
      <table width="100%" summary="Navigation footer">
        <tr>
          <td width="40%" align="left"><a accesskey="p" href="nestedtxn.html">Prev</a> </td>
          <td width="20%" align="center">
            <a accesskey="u" href="usingtxns.html">Up</a>
          </td>
          <td width="40%" align="right"> <a accesskey="n" href="txnindices.html">Next</a></td>
        </tr>
        <tr>
          <td width="40%" align="left" valign="top">Nested Transactions </td>
          <td width="20%" align="center">
            <a accesskey="h" href="index.html">Home</a>
          </td>
          <td width="40%" align="right" valign="top"> Secondary Indices with Transaction Applications</td>
        </tr>
      </table>
    </div>
  </body>
</html>
